Good evening. I'm terry moran. Thanksgiving's only two days away now, which means that holiday shopping frenzy is upon us. And if your christmas list is threatening to do major damage to your bank account, you're not alone. When it comes to finding the very best deals on everything from smartphones to cameras to toys, the answer may be only an app away. Abc's sharyn alfonsi brings us the new tricks to saving big for our series, "easy money." Reporter: Meet the perillo family. Three sisters in constant motion. It doesn't leave a lot of time for working parents, like sarah and chris perillo, to do a lot of holiday shopping. We look for online free shipping. Anything we can do to avoid the malls and bring three kids to the malls. Reporter: Increasingly, families like the perillos who struggle to find time to shop and the best deals are turning to the internet. This year, for the first time, more than half of us will shop online, spending $226 billion. In the true spirit of the season, we decided to bring them some high-tech help. Nice to meet you. Joanna stern is abc's tech editor. She showed us how to outsmart the stores to get great deals. On the perillos' list, a flat-screen tv and digital camera. We start looking. Is that really the price? Is it was this price this morning? Reporter: We were surprised to learn that prices online fluctuate from day-to-day and hour-to-hour. Watch in sony camera. The price dropped three times, $50, over the course of just 12 hours. When should you pull the trigger and buy? Tip number one, arm yourself with apps. At the store, we see a digital camera we were looking at. We want a step up. Reporter: And pull out our decide app. It scans the bar code, searching through thousands of pieces of information, to tell us whether we should buy it now or wait and get a better price later. It tells us to wait. But what about the samsung tv, on sale for $648. It says buy. So, sarah does. On the toy aisle, we saw bouncing tigger. It's at the top of the girls' list. That's not going to make you crazy? It definitely will. Reporter: It was $39.99 at target, marked down to $28.99. Click to compare. Using another app, called red laser, we scan the bar code and find it per. Target will match online pricing this year, so we get it for $21. Know the trends. And those who analyze them, say unless you're trying to scoop up a hot-selling toy, you can steer clear of the toy aisle this black friday. Toys will be at their lowest prices two weeks before christmas. And typically, the best time to buy appliances will be monday. Travel deals tuesday. Julie wednesday. Clothing thursday. But if you're shopping online and don't like the price, tip number four, just walk away. If you put something in your cart and you walk away from it, it's playing hard to get. Tell them what you want, walk away. And they might lower the price. Send an e-mail and say, we insided you had this in your cart, here's the 10% . Reporter: To trick the computer, you may need to put in your credit card number. But don't use it. It's not about clicking on it and going away. We have to go to the very last step before you click place the order? Exactly. Reporter: And the discounts keep coming. The perillos saved $390. Proving that you can crack the codes an get great deals. But hiding the gifts, that's still an old-fashioned artform. For "nightline," I'm sharyn

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